Bioluminescence imaging with luciferase enzymes requires access to light-emitting, small molecule luciferins. Here, we describe a rapid method to synthesize d-luciferin, the substrate for firefly luciferase (Fluc), along with a novel set of electronically modified analogs. Our procedure utilizes a relatively rare, but synthetically useful dithiazolium reagent to generate heteroaromatic scaffolds in a divergent fashion. Two of the luciferin analogs produced with this approach emit light with Fluc in vitro and in live cells. Collectively, our work increases the number of substrates that can be used for bioluminescence imaging and provides a general strategy for synthesizing new collections of luciferins.

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The phosphorylation state and corresponding activity of the retinoblastoma tumor suppressor protein (Rb) are modulated by a balance of kinase and phosphatase activities. Here we characterize the association of Rb with the catalytic subunit of protein phosphatase 1 (PP1c). A crystal structure identifies an enzyme-docking site in the Rb C-terminal domain that is required for efficient PP1c activity towards Rb. The phosphatase-docking site overlaps with the known docking site for Cyclin dependent kinase, and PP1 competition with Cdk-Cyclins for Rb binding is sufficient to retain Rb activity and block cell cycle advancement. These results provide the first detailed molecular insights into Rb activation and establish a novel mechanism for Rb regulation in which kinase and phosphatase compete for substrate docking.

Bioluminescence imaging with luciferase-luciferin pairs is commonly used for monitoring biological processes in cells and whole organisms. Traditional bioluminescent probes are limited in scope, though, as they cannot be easily distinguished in biological environments, precluding efforts to visualize multicellular processes. Additionally, many luciferase-luciferin pairs emit light that is poorly tissue penetrant, hindering efforts to visualize targets in deep tissues. To address these issues, we synthesized a set of π-extended luciferins that were predicted to be red-shifted luminophores. The scaffolds were designed to be rotationally labile such that they produced light only when paired with luciferases capable of enforcing planarity. A luciferin comprising an intramolecular “lock” was identified as a viable light-emitting probe. Native luciferases were unable to efficiently process the analog, but a complementary luciferase was identified via Rosetta-guided enzyme design. The unique enzyme–substrate pair is red-shifted compared to well-known bioluminescent tools. The probe set is also orthogonal to other luciferase-luciferin probes and can be used for multicomponent imaging. Four substrate-resolved luciferases were imaged in a single session. Collectively, this work provides the first example of Rosetta-guided design in engineering bioluminescent tools and expands the scope of orthogonal imaging probes.

A light-activated NO donor, [Mn(PaPy3)(NO)]ClO4 (1a), has been incorporated into HEMA-based polymer hydrogel and the nitrosyl-polymer conjugate materials 1ax · HG and 1ax · HGMB have been characterized. The NO releasing properties and antibacterial capabilities of these materials in conjunction with growth attenuators such as hydrogen peroxide and methylene blue (MB) are reported. Since the nitrosyl releases NO only upon exposure to light, materials like 1ax · HGMB could be used as wound dressings that deliver NO under controlled conditions.